Patent document 1 discloses a system, in which a handheld electronic key and an in-vehicle system communicate with each other to collate an ID code and a door of the vehicle is locked/unlocked based on the collation result. In the system, a transmitter of the in-vehicle system has given detection areas outside and inside of the vehicle and transmits request signals within the detection areas with given intervals. Thus, the system monitors a holder of the handheld unit, who approaches the vehicle or gets in/out the vehicle.
For instance, the holder of the handheld unit approaches the vehicle for getting in and enters the detection area. Then, upon receiving a request signal, the handheld unit transmits to the in-vehicle system a response signal including an ID code. When the in-vehicle system verifies the ID code, e.g., determines that the received ID code accords with a registered ID code, it sends a control signal to a door control unit for each door to be in a standby state ready for unlock. In the standby state, a touch sensor in a door handle is supplied with an electric current, which allows detection of the holder who touches the door handle. When the touch sensor detects an operation for the holder to touch the door handle, the door control unit unlocks each door.
Further, when the engine of the vehicle stops and the holder gets out the vehicle, the handheld unit is located in the detection area outside of the vehicle. Thus, when the ID code of the handheld unit is verified and a door lock switch nearby the door handle is then operated, the door is locked.
In the above system, the holder of the handheld unit can lock/unlock the door without actually holding the handheld unit by hand. This increases user's convenience.
For instance, the holder of the handheld unit may remain nearby the vehicle, e.g., when the holder washes or fixes the vehicle. In this case, the in-vehicle system transmits request signals to the detection area outside of the vehicle with intervals. Thus, the handheld unit nearby the vehicle frequently returns response signals to the in-vehicle system and the in-vehicle system collates the ID code. This consumes electric power in both the handheld unit and in-vehicle system. Further, a water splash due to washing the vehicle may reach the door handle to thereby activate the touch sensor and resultantly release the door lock of the vehicle.
Furthermore, the vehicle may include a security unit for preventing a theft of the vehicle. The security unit has a sensor to detect vibrations or sounds arising from a force applied to the parked vehicle and output an alarm. Such a security unit is typically activated to monitor when the occupant gets out the vehicle and locks the door.
However, for instance, when the vehicle is washed by the holder, the security unit may unnecessarily output the alarm in response to the vibrations or sounds. The security unit is typically designed to have a switch for turning on/off; however, the switch is provided inside of the vehicle. Therefore, to operate the switch inside the vehicle for tuning off the system is burdensome.                Patent document 1: JP-2006-28838 A (US-2006/0012462 A1)        